Eccrine sweat glands will be obtained from the monkey palm, rat paw, mouse paw and from normal human skin and from skin biopsies from patients with cystic fibrois. A segment of the secretory coil will be dissected and mounted on a double or triple coaxial micropipet. In vitro factors for influencing the secretory activity of an isolated secretory coil will be thoroughly studied. These include osmolarity, serum factor, colloid, nutrient, electrolytes, temperature, plt, buffer, etc. The permeability characteristics of the secretory epithelia will be studied by measuring the transepithelial flux of radioactive isotopes of varying molecular size and chemical characteristics. Transepithelial electrical potential difference (P.d.) will be measured in resting and in stimulated states. The response of P.d. to ionic substitution in the incubator medium will also be performed. The transepithelial conduction will be measured by injecting current pulses into an isolated short segment of the secretory coil.